High voltage direct current relays are mostly mounted on buses and new energy vehicles. During the operation, the high voltage direct current relays will generate outwardly side-blown arcs. However, in the case where the cathode and anode of a high voltage direct current relay are connected inversely or vehicles such as buses brake suddenly, each set of movable and fixed contacts of the high voltage direct current relay will blow arcs inward, and opposite arcs will be generated between two sets of movable and fixed contacts. Once the opposite arcs come into contact with each other, the high voltage direct current relay is likely to be short-circuited, thereby resulting in fire, explosion or other accidents.